Safety-fuse for electric circuits.



110.859,54?. PATBNTBD JULY 9, 19o?.

' C. s. DAVIS.

SAFETY FUSE FOR ELECTRIC CIRCUITS.

APPLIOATION FILED 0012x1905. RBNBWED D110. 7. 190e.

of Miene-sei' 'slid ITEI) STATES specification of Letters Patent.

PATENT ernten.

.sEriiv-,FUSE non ELECTRIC erneutes.

Patented 5111519, i907.,v

' lApplisation filed October 27, 1905. `ltenewed December?, IQS. Serial No. 846.805.

Beitknown that I, GHiinnnsKSwDAvis, a citizen of the 'United States I 1 y u tts,"have invented an Improvement in F-usesflor Electric Circuits, of which the following.descriptionyin connection with the" accompanying drawings, `:is a"`spec"ification, like letterson the drawings representing like parts.

The present invention relates to a safety fuse for electric circuits, and is embodied in a fuse of the socalled cartridge type in which,the'wdestructible or fusible portion is inclosed in a casing land usually surrounded with some finely divided gas-absorbing material which is packed tightly into the casing. The material commonly used is powdered chalk, some asbestos usually being employed near the ends Kof the casing to prevent the powdered material from sifting through the vent openings, with which the ends are commonly provided. So far as relates to the present invention, however, it is sufficient to describe the fuse as contained in an inclosed casing.

The purpose of the invention is to construct the fuse in such a manner that the casing may be repeatedly used, and a new strip of fusible material applied-thereto without the exercise of special skill or the use of special tools. The body of the casing fora fuse of this description is commonly made of fiber, or similar substance, in cylindrical form, and the ends of the casing are inclosed by metallic caps extended over the ends of the fiber tube, the said caps being provided with terminals or extensions, while the fusible strip ex.- tends through the tube from one extension to the other.

@heee extensions are commonly known in the art as knife blade terminals. 'Ihe fusible strip thus inclosed is usually closely packed in a mass of gas-absorbing material which wholly fills the casing.

In accordance with the present invention, the metallic caps at the ends of the casing are pro vided with y openings for the ends of a fusible strip which is longer than the casing so as to extend through the saine and project outward through the openings at both ends. These projecting ends of the fusible strip are connected with the caps at the outside of the casing so as to be readily accessible for removal. Furthermore, the caps themselves are so connected with the body of the casing as to be readily removable therefrom and easily replaceable, so that when a fuse has been blown, a new fuse can be easily inserted, thus utilizing the original casing. Figure l is an elevation, partly in section, of a-fuse embodying the invention; Fig. 2 is a longitudinal section, on a plane transverse to that of the section in Fig. l; and Fig. 3 a partial perspective view. The body a of the casing is -shown as consisting of a cylinder or tube, which may be made of fiber board, or other non-conducting substance, the said casing being rvtillefin the county closed at the ends by means of metallic cup-shaped caps b which may be fastened in any siiitable way, the connecting device, to be hereinafter described, serving, in the construction'embodying the invcntimi, jas a Sullicient fastening, although Iprefer to use, in addition, a bayonet joint, as indicated at b. The ,ends of the casing, e., in the construction shownl` `the caps b, are slotted across the middle, as indicated at b3, and provided at a point adjacent to the slot with'lrnife blade" terminals or extensions b4 for connecting the fuse'iri the circuit to be4 protected. These terminals project from the ends of the casing and may form an integral i part thereof, and, in the construction herein shown, (Fig. 2), consist of metal strips which project through the Islots bsfand are bent over into contact with the inner surfaces of the caps an'd secured thereto, as by solder, or rivets, b5, or both. The fusible strip c is made longer than the casifng, and extends completely through the same, projecting outward through the slots b3 at'opposite ends adjacent to the terminals b4. rIhe projecting end portions c2 are herein shown fastened outside the casing in electrical contact with the terminals b1 by readilyH detachable fastening devices, these end portions for example being clamped between washers c3 and the terminals b4 by 'means ofscrews cL and nuts c5. The fusible strip c is shown as embedded in gas-absorbing material g, such as powdered chalk, or any suitable chemical, with which the 'casing is tightly packed. The ends of the caps b are shown as provided with vent openings b,` and to prevent the powdered substance from sifting out, a small quantity of fibrous asbestos may-be packed in at the ends, as indicated at g2. y' r It will be seen, frm the foregoing description, that when a fuse blows out, it is a simple matter to removethe ends `of the destroyed fuse from the outside of the caps b which may then be removed for the insertion of a new fuse, and the repacking of thc casing.

The bayonet joints indicated at Z;2 serve kmerely to prevent the caps from being blown off, by the expansion of the gases, when the fuse blows, since it is obvious that when the fuse is complete7 the caps are held in vplace by the fastenings at the end thereof.

lIn assembling the fuse, the fusible strip c packed in the case is so positioned that the ends thereof will be alined with the slots when the caps are in such posi. tion that the projecting part of the bayonet joint .will bein line with the longitudinal portion of the channel in the casing. The caps can then be pushed into i place, and the casing itself given a turn to the position shown in Fig. l, thus securing the caps against endwise displacement without twisting or injuring the fuse:\A

It'is not intended to limit the invention to the spe cific construction and arrangement herein shown and described, especially so far as relates to the casing and sie ` within said casing around said fusible member; and removable fastening devices outside of the casing for ho ding the ends of said fusible member in electrical contact with said projecting portions.

2. In a safety fuse for electric circuits, the c0mbination .with a cylindrical casing; of inclosing caps at the ends of said casing, said inciosing caps being provided with slots extending transversely across the same; metallic terminal projections adjacent to said slots; a fusible strip extendingthrough said casing and projecting outward through said. slots; washersextending over said terminal projections;,and 'removable devices for clamping said projecting ends between said Washers and said projecting terminal portions, substantially as described.

3. ln an inclosed fuse and casing, a fusible member extending through said casing and projecting out beyond the ends thereof; projecting portions ot conducting material at the ends of.th e casing; and external removable fastening devices for securing the ends ot said fusible member to said projecting portions.

4. ln an inclosed fuse, a main casing of insulating material; inclosing caps for the ends of said casing provided with projections and slots adjacent thereto; a strip of fusible material ertending through the casing and projecting through the slots, and being.: electrically connected with the projections; and a bayonet joint to prevent endwise displacement of the caps.

5. In an inclosed lle'd fuse o! the cartridge type, the combination with the casing; of removable und replaceable caps provided with knife blade terminals and with slotsadjacent to said terminals; and :i fusible strip extending through the casing and the'slots of the cups, and attached to the caps at the outsides thereof.

in testimony whereof. 1 have signed my name to this specification in the presence of two subscribing witnesses CHARLES S. DAVIS.

Witnesses:

M. E. COVENEY, HENRY J. LIVERMORE. 

